Portland cement is the most common type of cement in general use around the world. Portland cement is composed essentially of compounds of lime (CaO) mixed with silica (SiO2) and alumina (Al2O3). The lime is typically obtained from a calcareous (lime-containing) raw material, and the silica and alumina are typically obtained from an argillaceous (clay) material.
Due primarily to the presence of lime, Portland cement is caustic, and can cause chemical burns to the user's skin. The powder can cause irritation and prolonged exposure can cause lung cancer. Additional environmental concerns include high energy consumption needed to mine, manufacturer and transport the cement, and the related air pollution resulting from the release of CO2, dioxin, NOx, SO2, and particulates.
U.S. Pat. No. 8,137,454 to McPherson discloses a cement composition that includes at least 60% by weight fine and/or coarse glass aggregate. The composition is used for high density, low porosity sheet forming materials where low hydraulic permeability and high compressive and tensile strength are desired. In addition to the glass aggregate, the cement composition includes required amounts of conventional cement (e.g. Portland cement or white cement) and pozzolans. The described Portland cement has a CaO content of 65% by weight. The described pozzolans include wollastonite having a CaO content of 48% by weight and ground granulated blast furnace slag having a CaO content of 39% by weight. Similar cement compositions are disclosed in U.S. Pat. Nos. 7,771,529 and 8,480,802, both to McPherson.
There is a need or desire for a concrete composition that is both environmentally safe and chemically inert, and is useful in a wide variety of corrosive environments.